Re: [PATCH v4 0/2] iio: adc: Add Maxim MAX11100 driver

Hi Jonathan,

On 15/01/2017 15:31, Jonathan Cameron wrote:

On 15/01/17 14:13, jacopo mondi wrote:

quoted

Hi Jonathan,
   thanks for review,

On 13/01/2017 10:50, Jacopo Mondi wrote:

quoted

Hello,
   sending out v4 splitting device tree bindings documentation and actual ADC
driver.
No changes in driver code since v3.

Same question for iio maintainers here:
I would like to have clarified the measure unit returned by read_raw().
Currently (value_raw * value_scale) return the ADC input value in mV.

Good.

quoted

quoted

While testing the patch I've been questioned if that should not actually
be in uV. This is easily achievable making _scale return a value in uV.
I have found no mention of this in the ABI documentation as it speaks of
generic voltage. Can we have a final word on this?

I see you have reviewed the driver without complaining for the
read_raw() measure unit, so I assume this replies to the above
question as well...

The units are specified in Documentation/ABI/testing/sysfs-bus-iio.

quoted

What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_raw
What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_supply_raw
What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_i_raw
What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_q_raw
KernelVersion:	2.6.35
Contact:	linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Description:
		Raw (unscaled no bias removal etc.) voltage measurement from
		channel Y. In special cases where the channel does not
		correspond to externally available input one of the named
		versions may be used. The number must always be specified and
		unique to allow association with event codes. Units after
		application of scale and offset are millivolts.

So millivolts.  This comes from a, perhaps ill judged, decision to match
hwmon units were we could.

Thank you! The "generic voltage" I said is mentioned in the ABI documentation is in _scale attributes description.
I assume then the measure unit of the value returned by _scale is not relevant as long as the _raw one with scale applied  returns millivolts.

Thanks, as soon as I have feedbacks on DTS binding docs, I'll send v5 and we can hopefully close this one ;)

Thanks
   j

Jonathan

quoted

Thanks j

quoted

Thanks Marek for having tested this.

v1 -> v2:
    - incorporated pmeerw's review comments
    - retrieve vref from dts and use that to convert read_raw result
      to mV
    - add device tree bindings documentation

v2 -> v3:
    - add _SCALE bit of read_raw function and change _RAW bit accordingly
    - call regulator_get_voltage when accessing the _SCALE part of read_raw
      and not during probe
    - add back remove function as regulator has to be disabled when detaching
      the module. Do not use devm_ version of iio_register/unregister functions
      anymore but do unregister in the remove.
    - remove mutex as access to SPI bus is protected by SPI core. Thanks marex

v3 -> v4:
    - split device tree binding documentation and actual ADC driver
    - add "reg" to the list of required properties and use a better
      namimg for the adc device node in bindings documentation as suggested
      by Geert.

Jacopo Mondi (2):
  iio: adc: Add Maxim MAX11100 driver
  dt-bindings: iio: document MAX11100 ADC

 .../devicetree/bindings/iio/adc/max11100.txt       |  19 +++
 drivers/iio/adc/Kconfig                            |   9 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/max11100.c                         | 187 +++++++++++++++++++++
 4 files changed, 216 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/max11100.txt
 create mode 100644 drivers/iio/adc/max11100.c